高气压MPCVD沉积金刚石的光谱研究

采用微波等离子体化学气相沉积方法(microwave plasma chemical vapor deposition, MPCVD)在高沉积气压(34.5 kPa)下制备多晶金刚石，利用发射光谱(optical emission spectroscopy, OES)在线诊断了CH₄/H₂/O₂等离子体内基团的谱线强度及其空间分布，并利用拉曼(Raman)光谱评价了不同O₂体积分数下沉积出的金刚石膜质量，研究了金刚石膜质量的均匀性分布问题。结果表明：随着O₂体积分数的增加，C₂, CH及H_α基团的谱线强度均呈下降的趋势，而C₂，CH与H_α谱线强度比值也随之下降，表明增加O₂体积分数不仅导致等离子体中碳源基团的绝对浓度下降，而且碳源基团相对于氢原子的相对浓度也降低，使得金刚石的沉积速率下降而沉积质量提高。此外，具有刻蚀作用的OH基团的谱线强度却随着O₂体积分数的增加而上升，这也有利于降低金刚石膜中非晶碳的含量。光谱空间诊断发现高沉积气压下等离子体内基团分布不均匀，特别是中心区域C₂基团聚集造成该区域内非晶碳含量增加，最终导致金刚石膜质量分布的不均匀。

Optical Spectroscopy for High-Pressure Microwave Plasma Chemical Vapor Deposition of Diamond Films

Polycrystalline diamond growth by microwave plasma chemical vapor deposition (MPCVD) at high-pressure (34.5 kPa) was investigated. The CH₄/H₂/O₂ plasma was detected online by optical emission spectroscopy (OES), and the spatial distribution of radicals in the CH₄/H₂/O₂ plasma was studied. Raman spectroscopy was employed to analyze the properties of the diamond films deposited in different oxygen volume fraction. The uniformity of diamond films quality was researched. The results indicate that the spectrum intensities of C₂，CH and H_α decrease with the oxygen volume fraction increasing. While the intensity ratios of C₂，CH to H_α also reduced as a function of increasing oxygen volume fraction. It is shown that the decrease of the absolute concentration of carbon radicals is attributed to the rise volume fraction of oxygen, while the relative concentration of carbon radicals to hydrogen atom is also reducing, which depressing the growth rate but improving the quality of diamond film. Furthermore, the OH radicals, role of etching, its intensities increase with the increase of oxygen volume fraction. Indicated that the improvement of OH concentration is also beneficial to reduce the content of amorphous carbon in diamond films. The spectrum space diagnosis results show that under high deposition pressure the distribution of the radicals in the CH₄/H₂/O₂ plasma is inhomogeneous, especially, that of radical C₂ gathered in the central region. And causing a rapid increase of non-diamond components in the central area, eventually enable the uneven distribution of diamond films quality.